Latent heat storage units with or without mixing containers are the subject matter of numerous patents or patents applications such as, for example, German patent application DE 43 14 509 A1 or German patent specification DE 2607168 C3 as well as U.S. Pat. No. 4,111,260 A, German patent application DE 10 2013 208974 A1 and U.S. Pat. Appln. No. 2012/168126 A1. With methods of this type, the essential step is that, during the withdrawal of energy from the heat storage unit, the solidifying or solidified heat storage fluid is reliably and completely separated from the liquid heat storage fluid and especially, both of them are completely separated from the heat transfer fluid, since the heat transfer fluid is constantly being cooled to temperatures that are below the solidification temperature of the heat storage fluid, and consequently, the external heat exchanger that serves to cool the heat transfer fluid becomes clogged with solid heat storage fluid if the heat storage fluid is not removed completely from the heat transfer fluid. The reliable separation of solid and liquid heat storage fluid is of importance since liquid heat storage fluid is constantly needed in order to be brought into contact with the heat transfer fluid, whereby solid heat storage fluid only disrupts this process if it is unnecessarily moved and if it also becomes mixed with the heat transfer fluid once again. Moreover, as a rule, the heat transfer fluid—in this case, preferably kerosene or octane—is much more expensive than the heat storage fluid—in this case, preferably water—so that the amount of heat transfer fluid in the process should be kept as small as possible and above all, the zones where heat transfer fluid and heat storage fluid are present in mixed form should be kept as small as possible. German patent application DE 43 14 509 A1 repeatedly points out that the above-mentioned separation problem is of the essence for the method and for the device. In German patent specification DE 2607168 C3, it was recognized that, in the final analysis, the separation of heat transfer fluid and heat storage fluid is the crux of all of the methods that deal with this topic. If this separation cannot be achieved with simple measures, then, for all practical purposes, these methods cannot be used, which is why none of the patented methods have found use on a large scale. German patent application DE 43 14 509 A1 also describes how a separation of heat transfer fluid and heat storage fluid can be achieved by means of a coalescer.
U.S. Pat. No. 4,111,260 A does not discuss at all how the heat transfer fluid and the heat storage fluid can be separated from each other. U.S. Pat. Appln. No. 2012/168126 A1 does not encounter the problem of the separation of heat transfer fluid and heat storage fluid since there, the heat-storing material is enclosed in the heat storage container, as a result of which this construction entails the usual drawbacks that arise when heat is transferred from one fluid to another fluid or to a solid. German patent application DE 10 2013 208974 A1 does not elaborate upon the details of the separation of the heat storage fluid (or heat storage solid) and the heat transfer fluid, in addition to which this document relates to a different heat transfer fluid.